Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$102.35	9.786%	$112.366	$112.37	$112.35	$112.40
Purchase #2	$98.37	11.651%	$109.8311	$109.83	$109.85	$109.80
Purchase #3	$101.88	10.419%	$112.4949	$112.49	$112.50	$112.50
Purchase #4	$103.55	6.123%	$109.8904	$109.89	$109.90	$109.90
Purchase #5	$50.80	6.121%	$53.9095	$53.91	$53.90	$53.90
Purchase #6	$9.62	7.725%	$10.3631	$10.36	$10.35	$10.40
Purchase #7	$162.45	13.588%	$184.5237	$184.52	$184.50	$184.50
7 purchase totals =	$629.02		$693.3787	$693.37	$693.35	$693.40